Question

Is it possible to use TastyPie to update a ForeignKey field to None?

Related question: tastypie won't remove foreignkey reference during PUT

What I have:

class SomeObject(models.Model):
    some_field = models.ForeignKey(SomeOtherObject, null=True)

(and of course the corresponding TastyPie resource class that works fine for updating other fields)

What I want:

To update some_field to None using TastyPie.

What I’ve tried (in JavaScript):

$.put('/my/api/model/someobject/42/', { some_field: null });
$.put('/my/api/model/someobject/42/', { some_field: '/my/api/model/someotherobject/null/' });
$.put('/my/api/model/someobject/42/', { some_field: '' });
$.put('/my/api/model/someobject/42/', { some_field: 0 });
$.put('/my/api/model/someobject/42/', { some_field: false });

And so on. These all result in 404 or 400. Some result in 204, but the database is not updated.

Reading through the code in full_dehydrate(), it seems it might not be possible at present do so.

I’ve looked at the recent code on github, and I’m not convinced this is possible.

Answer 1

Here is a generic solution. Create a base resource and extend all other resources from this one. It’s a hack, but it works.

class MyResource(ModelResource):
    def obj_update(self, bundle, request=None, **kwargs):
        for field_name in self.fields:
            field = self.fields[field_name]

            if type(field) is ToOneField and field.null and bundle.data[field_name] is None:
                setattr(bundle.obj, field_name, None)

        return super(MyResource, self).obj_update(bundle, **kwargs)